Long-term variations in population structure,growth,mortality,length at median sexual maturity,and exploitation rate of threadfin bream(Nemipterus virgatus)are reported based on bottom trawl survey data collected duri...Long-term variations in population structure,growth,mortality,length at median sexual maturity,and exploitation rate of threadfin bream(Nemipterus virgatus)are reported based on bottom trawl survey data collected during 1960-2012 in the Beibu Gulf,South China Sea.Laboratory-based analyses were conducted on 16791 individuals collected quarterly in eight different sampling years.Average body length,estimated asymptotic length,and percentage of large individuals have decreased significantly with the growth of marine catch and fishing power,indicating individual miniaturization of this fish species.Estimated exploitation rates indicate that the N.virgatus stock in the Beibu Gulf was moderately exploited in 1960 and 1962 and overexploited after 1992.This stock was taking a good turn in status in 2012,with the lowest exploitation rate since 1992 and ceased downward trend in length indexes.These results suggest that management measures to reduce fishing pressure may have a positive influence on the biological characteristics of this commercial fish species.Biological characteristics of most commercial fish species have phenotypic plasticity and might change over years in response to fisheries management.Therefore,attentions should be paid on variations in fish biological characteristics,when evaluating the effectiveness of current measures to control the total catch for all fisheries.展开更多
A single three point bend specimen compliance method for determining JIC of high strength high fracture toughness steels is presented and a formula for calculatinff J-integral is proposed as follows.It is simple and v...A single three point bend specimen compliance method for determining JIC of high strength high fracture toughness steels is presented and a formula for calculatinff J-integral is proposed as follows.It is simple and valid for high strength high fracture toughness steels. The values of JIC and KIC measured by this method are in good agreement with those measured by standard test method.展开更多
The dislocation momentum is the design basis for anti-dislocation to tunnel when a tunnel crosses an active fault.The influence of different dislocation levels on tunnel performances is not clear.Thus,based on seismic...The dislocation momentum is the design basis for anti-dislocation to tunnel when a tunnel crosses an active fault.The influence of different dislocation levels on tunnel performances is not clear.Thus,based on seismic activity parameters at the site of interest and probability of fault dislocation,probability fault displacement hazard analysis(PFDHA)methodology was introduced in this paper to ascertain the fault dislocation level under different exceeding probabilities(63%,10%,and 2%–3%).Then,based on the definition of different ground motion strength and fortification goals of the tunnel,a three-level fortification goal with different performance requirements of the tunnel was proposed.The first attempt to use the proposed indexes including the maximum dislocation of the tunnel and maximum relative deformation of the tunnel was tried to evaluate deformation and failure states with an experimental approach.Subsequently,the feasibility of the three-level fortification goal was further investigated according to the self-defined qualitative description and quantitative indexes in the segmental design and sectional expansion tunnels comprehensively.The results show that the fault dislocations relying on PFDHA at the site of the Shantou Submarine Tunnel are firstly ascertained as 0.04,1.8,and 2.4 m respectively.Taking the fault dislocation as model input values into account,the dislocation mechanism of the tunnel under the three levels was revealed.More importantly,judging from the dislocation performance requirements of the three-level fortification goal,the tunnel deformation and failure states are mitigated by adopting the countermeasures.The sectional expansion design can well meet the requirements without the restriction of a strong earthquake,while the effectiveness of the segmental tunnel can be proved under frequently occurred and fortification earthquake.The final research results are expected to provide a new fortification goal for anti-dislocation hazard evaluation on expansion design in high-intensity seismic regions and segmental design in slight and moderate-intensity seismic regions.展开更多
With the rapid development of urban traffic networks,subway stations will inevitably be constructed close to other structures in the future.The subject of this study is a new subway station in China,combined with a fl...With the rapid development of urban traffic networks,subway stations will inevitably be constructed close to other structures in the future.The subject of this study is a new subway station in China,combined with a flyover standing on the roof,owing to its unique structural design.Based on the time history-analysis method,the dynamic responses of the subway station,piers,and piles under seismic conditions were examined.The results show that the internal force and deformation of the underground structure vary under seismic excitation in different directions and are more dangerous in the under transverse excitation than under longitudinal excitation.Moreover,the dynamic response of the underground structure is severe under the action of low-frequency-rich Wenchuan waves,and the resonance effect is distinct.The load of the bridge was found to inhibit the deformation of the underground structure to a certain extent.Furthermore,the mid-pillar and slab-mid-pillar connections are the weakest parts,and special attention should be paid to their seismic design.Meanwhile,the piers and piles can maintain good working condition under the action of an earthquake with the peak acceleration of 0.1g.展开更多
基金The National Key R&D Program of China under contract No.2018YFD0900906the National Natural Science Foundation of China under contract No.31602157+1 种基金the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory under contract No.GML2019ZD0605the Central Public-Interest Scientific Institution Basal Research Fund under contract Nos 2020TD05 and 2021SD01。
文摘Long-term variations in population structure,growth,mortality,length at median sexual maturity,and exploitation rate of threadfin bream(Nemipterus virgatus)are reported based on bottom trawl survey data collected during 1960-2012 in the Beibu Gulf,South China Sea.Laboratory-based analyses were conducted on 16791 individuals collected quarterly in eight different sampling years.Average body length,estimated asymptotic length,and percentage of large individuals have decreased significantly with the growth of marine catch and fishing power,indicating individual miniaturization of this fish species.Estimated exploitation rates indicate that the N.virgatus stock in the Beibu Gulf was moderately exploited in 1960 and 1962 and overexploited after 1992.This stock was taking a good turn in status in 2012,with the lowest exploitation rate since 1992 and ceased downward trend in length indexes.These results suggest that management measures to reduce fishing pressure may have a positive influence on the biological characteristics of this commercial fish species.Biological characteristics of most commercial fish species have phenotypic plasticity and might change over years in response to fisheries management.Therefore,attentions should be paid on variations in fish biological characteristics,when evaluating the effectiveness of current measures to control the total catch for all fisheries.
文摘A single three point bend specimen compliance method for determining JIC of high strength high fracture toughness steels is presented and a formula for calculatinff J-integral is proposed as follows.It is simple and valid for high strength high fracture toughness steels. The values of JIC and KIC measured by this method are in good agreement with those measured by standard test method.
基金supported by the National Natural Science Foundation of China(No.52130808)the National Key Research and Development Program of China(No.2022YFE0104300)。
文摘The dislocation momentum is the design basis for anti-dislocation to tunnel when a tunnel crosses an active fault.The influence of different dislocation levels on tunnel performances is not clear.Thus,based on seismic activity parameters at the site of interest and probability of fault dislocation,probability fault displacement hazard analysis(PFDHA)methodology was introduced in this paper to ascertain the fault dislocation level under different exceeding probabilities(63%,10%,and 2%–3%).Then,based on the definition of different ground motion strength and fortification goals of the tunnel,a three-level fortification goal with different performance requirements of the tunnel was proposed.The first attempt to use the proposed indexes including the maximum dislocation of the tunnel and maximum relative deformation of the tunnel was tried to evaluate deformation and failure states with an experimental approach.Subsequently,the feasibility of the three-level fortification goal was further investigated according to the self-defined qualitative description and quantitative indexes in the segmental design and sectional expansion tunnels comprehensively.The results show that the fault dislocations relying on PFDHA at the site of the Shantou Submarine Tunnel are firstly ascertained as 0.04,1.8,and 2.4 m respectively.Taking the fault dislocation as model input values into account,the dislocation mechanism of the tunnel under the three levels was revealed.More importantly,judging from the dislocation performance requirements of the three-level fortification goal,the tunnel deformation and failure states are mitigated by adopting the countermeasures.The sectional expansion design can well meet the requirements without the restriction of a strong earthquake,while the effectiveness of the segmental tunnel can be proved under frequently occurred and fortification earthquake.The final research results are expected to provide a new fortification goal for anti-dislocation hazard evaluation on expansion design in high-intensity seismic regions and segmental design in slight and moderate-intensity seismic regions.
基金the financial support from the National Natural Science Foundation of China(Grant No.51878566)the Sichuan Science and Technology Program(Grant No.2019YFG0001)Sichuan Science and Technology Key R&D Project(Grant No.2020YFS0294).
文摘With the rapid development of urban traffic networks,subway stations will inevitably be constructed close to other structures in the future.The subject of this study is a new subway station in China,combined with a flyover standing on the roof,owing to its unique structural design.Based on the time history-analysis method,the dynamic responses of the subway station,piers,and piles under seismic conditions were examined.The results show that the internal force and deformation of the underground structure vary under seismic excitation in different directions and are more dangerous in the under transverse excitation than under longitudinal excitation.Moreover,the dynamic response of the underground structure is severe under the action of low-frequency-rich Wenchuan waves,and the resonance effect is distinct.The load of the bridge was found to inhibit the deformation of the underground structure to a certain extent.Furthermore,the mid-pillar and slab-mid-pillar connections are the weakest parts,and special attention should be paid to their seismic design.Meanwhile,the piers and piles can maintain good working condition under the action of an earthquake with the peak acceleration of 0.1g.
